//  添加按钮 和删除按钮
.mt {
    margin-top: 20px;

}


.mr {
    margin-right: 20px;
}

.ml {
    margin-left: 20px;
}

.center {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    margin: auto;

}